M56 is a faint distant globular cluster in Lyra positioned close to its border with Cygnus. At apparent magnitude +8.3, it's one of the dimmer Messier globulars and unlike most objects of its type lacks a bright core, resulting in it being a challenging binocular object. Nevertheless, the cluster is visible in small telescopes and amateur scopes of the order of 250mm (10-inch) will resolve some stars, despite its relatively large distance.
M56 was discovered by Charles Messier discovered on January 23, 1779. He described it as a "nebula without stars" and like many globular clusters was first resolved into stars by William Herschel five years later. Another unusual feature about this object is that it follows a retrograde orbit through the Milky Way. It has been suggested that M56 may have been acquired during the merger of a dwarf galaxy, of which Omega Centauri forms the surviving nucleus.
The globular is located almost halfway along an imaginary line connecting beautiful double star Albireo (β Cyg - mag. +3.1) with Sulafat (γ Lyr - mag. +3.3). However, since it's located in a dense part of the Milky Way it's easy to miss especially with small telescopes. Not far from M56 is the only other Messier object in Lyra, M57 the "Ring Nebula".
At best M56 appears as a faint slightly fuzzy star through 7x50 or 10x50 binoculars. It's obviously non-stellar when seen with larger 70 or 80mm models. A 100mm (4-inch) telescope shows the cluster as a faint, round, diffuse ball of light with very little or no detail discernible. A noticeable 5th magnitude star is located less than a degree northwest of the cluster. It's possible to resolve some of the outer stars using a 250mm (10-inch) telescope with the brightest members being of 13th magnitude. M56 displays a gradual, soft brightening from the outer regions towards the core. In total, the cluster measures 8.8 arc minutes across although visually it appears less than half this size. However, despite being overshadowed by M13 in Hercules, M56 is a fine globular in its own right.
M56 is 32,000 light-years distant, which corresponds to a spatial diameter of 84 light-years. It contains only a dozen or so variable stars and is estimated to be 13.7 billion years old. The globular is best seen from the Northern Hemisphere during the months of June, July and August.
M56 Data Table
|Object Type||Globular cluster|
|RA (J2000)||19h 16m 35s|
|DEC (J2000)||30d 11m 05s|
|Apparent Size (arc mins)||8.8 x 8.8|
|Number of Stars||80,000|
|Notable Feature||Moving in a retrograde orbit through the Milky Way|